This invention relates to devices that are subject to waves in the water, and that in some cases utilize the power of waves in water.
As a wave travels along the surface of water, it produces vertical motion, but no net horizontal motion, of water. The amplitude of the vertical motion decreases with depth; at a depth of about half the wavelength, there is little vertical motion. The speed of currents induced by wind also decreases sharply with depth. A number of proposals have been made to utilize wave power to do useful work. Reference may be made, for example, to U.S. Pat. Nos. 986,627, 1,315,267, 2,520,804, 3,312,186, 3,453,981, 3,508,516, 3,845,733, 3,872,819, 3,928,967, 4,332,571, 4,371,347, 4,389,843, 4,598,547, 4,684,350, 4,842,560, 4,968,273, 5,084,630, 5,577,942, 6,099,368 and 6,561,856, U.S. Publication Nos. 2003/0220027 and 2004/0102107, and International Publication Nos. WO 1987/04401 and WO 1994/10029. The entire disclosure of each of those patents and publications is incorporated herein by reference for all purposes.
Many of the known wave-powered devices (“WPDs”) comprise (1) a float, (2) a swimmer, and (3) a tether connecting the float and the swimmer; the float, swimmer, and tether being such that when the vehicle is in still water, (i) the float is on or near the surface of the water, (ii) the swimmer is submerged below the float, and (iii) the tether is under tension, the swimmer comprising a fin or other wave-actuated component which, when the device is in wave-bearing water, interacts with the water to generate forces that can be used for a useful purpose, for example to move the swimmer in a direction having a horizontal component (hereinafter referred to simply as “horizontally” or “in a horizontal direction”). The terms “wing” and “fin” are used interchangeably in the art and in this application.
It is desirable to position sensors and equipment in the ocean or lakes for long periods of time without using fuel or relying on anchor lines which can be very large and difficult to maintain. In recent years, the WPDs developed by Liquid Robotics, Inc. and marketed under the registered trademark Wave Glider®, have demonstrated outstanding value, particularly because of their ability to operate autonomously. It is noted that Wave Glider® WPDs are often referred to as Wave Gliders as a shorthand terminology. It is also noted that WPDs are often referred to as wave-powered vehicles (“WPVs”).